1. Field of the Invention
The present invention relates to an electric tilt adjustable steering apparatus for a vehicle with improved rigidity of a steering column in the vertical and horizontal directions.
2. Related Background Art
In an electric tilt adjustable steering apparatus for a vehicle, as shown in the prior Japanese Patent Application No. 2000-193227 owned by the assignee, or shown in FIGS. 3A and 3B, for instance, a tilt adjusting mechanism b is formed on one side of a steering column a for converting the rotational driving force of an electric motor to a rectilinear motion, thereby automatically adjusting the tilt of the steering column a. On the other side of the steering column a, a slide portion c is formed for sliding the steering column a in the vertical direction upon adjusting the tilt.
This slide portion c is arranged such that the left side of the steering column a is formed to be flat, and a plate d is attached to this flat surface. A flat block f is provided between this plate d and a flat internal wall of a housing e. Between the plate d and the block f, a roller h supported by a cage g is interposed.
With the above arrangement, when the steering column a is tilt-adjusted, the plate d slides on the flat surface of the block f through the rollers h, so that the steering column a can smoothly slide in the vertical direction.
It should be noted that a clamping bolt i is attached on the left wall of the housing e by means of a lock nut j and the clamping bolt i is clamped with a predetermined torque, so that a preload is applied in the right direction onto the block f. With this arrangement, backlash in the vertical direction and horizontal direction of the steering column a can be prevented.
However, since the electric tilt adjustable steering apparatus described above is arranged such that the plate d of the steering column a slides the block f through the rollers h, when a load is applied on the steering wheel in the vertical and horizontal directions, backlash of the steering column a in the vertical and horizontal directions can not always be prevented satisfactorily; hence the steering column a has low rigidity in the vertical and horizontal directions.
The present invention has been contrived taking the circumstances as mentioned above into consideration, and an object of the invention is to provide an electric tilt adjustable steering apparatus for a vehicle with the improved rigidity of the steering column in the vertical and horizontal directions.
In order to achieve the above object, according to the present invention, there is provided an electric tilt adjustable steering apparatus for a vehicle for automatically adjusting the tilt of a steering column by means of an electric motor so as to regulate an angle of inclination of the steering column to a desired one, comprising:
a tilt adjusting mechanism provided on one side of the steering column for converting a rotational driving force of the electric motor into a rectilinear motion so as to adjust the tilt of the steering column; and
a slide portion provided on the other side of the steering column which is in slidable contact with the stationary side by convex-concave fitting substantially in a triangular form, so as to slide the steering column upon tilt adjusting.
As described above, according to the present invention, since the slide portion is brought into contact with the stationary side by convex-concave fitting substantially in a triangular form, it is possible to smoothly slide the steering column in the vertical direction by sliding the slide portion on the convex-concave fitted portion substantially in a triangular form upon tilt adjusting.
Moreover, since the slide portion is brought into slidable contact by convex-concave fitting substantially in a triangular form, even when a load is applied on the steering wheel in the vertical direction and the horizontal direction, the backlash of the steering column in the vertical direction and the horizontal direction can be satisfactorily prevented, thereby enhancing the rigidity of the steering column.
Further, since the slide portion and the stationary side are brought into slidable contact with each other by convex-concave fitting substantially in a triangular form, it is possible to satisfactorily prevent the backlash of the steering column against the load from the steering wheel wherever the slide portion may slide with respect to the stationary side (or whatever the tilt angle may be).